Whether you’re new to hydroponics or just getting ready to start a new crop, you know that the growth medium you choose is incredibly important. There are several different grow media to choose from, but one of the most popular by far is clay pebbles. These pebbles are simply made by treating little balls of natural clay with high heat. Once fired, they provide a versatile growth medium that hydrates, aerates, and protects your plants. In this review, we’ll help you choose the ideal clay pebbles for your garden or growing operation.
Comparison Chart
Best Choice  | Grow !t GMC40l
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Also Great  | GEOLITE GMGC45L 45L Clay Pebbles
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Best Orchids  | CZ Garden Organic Expanded Clay Pebbles
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Best Hydroponics  | Mother Earth HGC714112 Hydroton Original Expanded Clay Pebbles
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Best Uniform-Size  | Hydro Crunch DBAUS888 Expanded Clay Growing Media
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Our Picks for Best Clay Pebbles.
1. Grow !t GMC40l – Best Budget Option Clay Pebbles For Home Gardening
Performance
These perform decently. They are very lightweight, so they are unlikely to crush or otherwise damage delicate root structures. In hydroponics, clay pebbles are not supposed to float once they are fully wet. In many cases, this product will still float. They aren’t reliable for hydroponics, but they should work well as a top layer for some potted plants like orchids.
Possible Reservations
Sometimes, these arrive looking different than advertised. Many are not round, and their pores become exposed over time as growers wash and reuse them. These pebbles then cling to the roots of the plants, making it significantly harder for them to absorb oxygen and nutrients. One of the benefits of clay pebbles is the fact that they can be rewashed and reused many times, so this is a significant drawback. Additionally, many pieces have sharp edges. We don’t recommend these for hydroponics, but they may work well in an outdoor traditional garden.
| Pros | Cons |
|---|---|
| They come in a large bag, so you’ll only need the one bag | They float even when wet |
| They are very lightweight | |
| They’re made from 100% natural clay | |
| The irregular shapes help the pebbles stick together |
2. GEOLITE GMGC45L 45L Clay Pebbles – Best Larger Operations Clay Pebbles For Outdoor Garden
Performance
These pebbles usually perform fairly well. Some growers may not like the highly irregular shapes, but they can neatly fill net pots and trays. They arrive with a lot of dust in the bag, so it’s advisable to rinse them thoroughly before use. Unfortunately, this product does not always expand, which can be a problem for some growing operations.
Possible Reservations
For growers who want pretty, uniformly-sized clay pebbles, these are not the option. Despite their shape irregularities, they work fairly well. We recommend these to growers who don’t really care about growth medium aesthetics.
| Pros | Cons |
|---|---|
| They are very affordable and come in a large bag | They do not expand in all cases |
| They are formed at high temperatures to avoid the risk of breaking down | |
| The manufacturer uses 100% Italian clay | |
| They drain very well |
3. CZ Garden Organic Expanded Clay Pebbles – Best Organic Option Clay Pebbles For Orchids
Performance
While this product is more expensive than most, it is also very high quality. The fact that they’re organic is a great bonus – you can be assured that they have not been exposed to pesticides, so your plants won’t be chemically damaged. They perform especially well when used with orchids because they drain well and encourage root aeration. You can use them for hydroponics, but some hydroponic growers would prefer that all of their pebbles are roughly the same size.
Possible Reservations
Customers who order this product have noted that they receive less than two pounds in the mail. CZ Gardens has a good customer service team, and they will typically send these buyers the rest of the pebbles they ordered promptly. The product that arrives does not look as nice and uniform as the picture on the product packaging. Most bags have far more small balls than large ones, although this is not necessarily a problem. We recommend these for smaller orchid growing operations and smaller hydroponic setups.
| Pros | Cons |
|---|---|
| This product isn’t exposed to pesticides, is pH-neutral, and is chemically inert | Some growers might not like the irregular sizes |
| The various sizes are ideal for growing orchids | Compared to some on the list, these are very expensive |
| The smaller pebbles are especially good for starting seeds | |
| Expanded clay acts as a water reservoir and releases extra water when roots need it |
4. Mother Earth HGC714112 Hydroton Original Expanded Clay Pebbles – Best Inert And pH-neutral Clay Pebbles For Hydroponics
Performance
These perform very well. Many buyers have commented on the lightness of the bag that arrives, and this indicates that the product is porous as advertised. They drain very well, and porousness is an excellent water reservoir. These also seem to hold up much longer than many other similar products, and they can be washed and reused many times.
Possible Reservations
While most growers who purchase these pebbles are very happy with them, there are some exceptions. Sometimes, the bag that arrives contains more irregular shapes than normal. Some growers have also said that they are prone to mold. Still, given the quality and the number of growers who are happy with them, we recommend these.
| Pros | Cons |
|---|---|
| These are more porous than many products, especially budget ones | They are a little more expensive than some products on the list |
| They are inert and pH-neutral | Some growers find that they are prone to mold growth |
| They have some variance in size, but they are almost all very round | |
| And they are durable and can be washed or reused again and again |
5. Hydro Crunch DBAUS888 Expanded Clay Growing Media – Best Uniform-Size Option Clay Pebbles Not For Flood-And-Drain Systems
Performance
These mostly perform well. Many customers have observed that they arrive with far less dust in the bag. This is because they are much harder than other clay balls and resist breaking or collapsing. Each bag that arrives is also lightweight, indicating that they are very porous. But they sometimes seem to be too porous – some growers find that these will still float even when wet.
Possible Reservations
The only real reservation we have about these is that some of them will float no matter how long they soak. For some hydroponic systems, this won’t be an issue, but floating can be enough to cause growers to look elsewhere. Still, this is an excellent quality product, and we recommend it.
| Pros | Cons |
|---|---|
| Given their high quality, they are very affordable | Some growes have issues with this product floating |
| They are much harder and more durable than many other products | Growers have complained that this product leaves a brown slime in the system |
| They arrive with much less dust in the bag than most media | |
| All pebbles in the bag are the same size |
Best Clay Pebbles – Buyer’s Guide
If you’re new to hydroponics, the sheer variety of growth media can be overwhelming. You can choose from vermiculite, Rockwool, coco coir, perlite, and several other options. Many beginners and experienced growers alike turn to clay pebbles, which are also called lightweight expanded clay aggregate (or LECA) or Hydroton. In this section, we’ll go over what you need to know to understand how this medium works and how to choose the type of clay pebbles for you.
How are Clay Pebbles Made?
The process of making these pebbles isn’t too intricate. Most manufacturers mass-produce these products, although some growers can make their own using less heat. Manufacturers first start with all-natural clay. In high-quality products, this clay doesn’t have any additives or fillers. Workers then form the clay into small balls. They heat them in a kiln at extremely high temperatures – usually 1100 to over 2000 degrees Fahrenheit.
In the process of heating, the balls “pop” much like popcorn does. The process gives the balls a larger circumference, and they develop pores as they pop. In a quality batch of pebbles, just about all of them will be round, but a few may have slightly irregular shapes.
What Makes Them a Good Growth Medium?
Clay pebbles are a very popular growth medium, and there are a lot of things that make them a good choice for a hydroponic garden. One of their best features is their porousness. They can act as water reservoirs for the plant. Since they are so close to the roots, it becomes easy for the plant to draw water and nutrient solution any time it’s needed.
The pores also mean that this medium is great for draining excess water. As you already know, hydroponically-grown plants that get plenty of water and not enough oxygen can drown in the water. As the porous pebbles absorb extra water, they stop that water from overwhelming the plant. Plus, their roundness means that there is space between each one. That space makes the medium much easier to drain.
To get an idea of why that space is important, imagining over-watering a plant in a pot with soil. If the soil is closely packed and becomes saturated, the plant may die. The water has nowhere to go. Clay pebbles can’t be packed like soil or sand, so the drainage process is fast and reduces the risk of over-watering.
Another reason why this is a good growth medium is the fact that they are pH-neutral. If you’re new to growing, you might wonder why this matters. An unbalanced pH in your growing medium can damage or even kill your plants. A pH that is too low will negatively impact root development because the plants become calcium deficient. A pH that is too high will result in stunted growth, although the exact effects are different depending on the type of plants you’re growing.
Some advertisers describe this product as being “EC stable.” EC stable means that they will not interfere with the electrical conductivity of your growing operation. Nutrient solutions almost always have a degree of electrical conductivity, and advanced growers can spend a considerable amount of time building up a plant’s internal electrical conductivity so it receives the optimal level of water and nutrients. We won’t get into electrical conductivity in too much detail, but the takeaway is that an EC-stable medium won’t interfere with this process.
Clay pebbles also are both cost-effective and environmentally friendly. A large bag of this medium may be somewhat expensive, but clay pebbles can be reused several times before they wear out and should be replaced. You do need to make sure they are thoroughly cleaned between uses – otherwise, bugs, pathogens, and even mold can be carried over to your next crop. To clean them thoroughly, start with a rinse with fresh water. After that, make up a solution of about 5% chlorine bleach. Let them soak in this solution for 24 hours – that should be enough to kill any pathogens.
After 24 hours, rinse them again thoroughly. Before using them again, it’s a good idea to buffer them with pH-corrected water to make sure they have returned to a neutral pH.
Lastly, clay has the advantage of being very pest-resistant. This is because most pests prefer to live in organic matter (like soil, coco coir, and pine shavings). It’s still wise to watch for pests and clean your pebbles after each use, but you should not encounter pests burrowing into your pebbles anytime soon.
What Are Some Potential Disadvantages?
Most growers seem to really like clay pebbles. But as with any growth medium, they do have some disadvantages. One of the most complained-about disadvantages is the dust that comes with them when they first arrive. The dust occurs during the shipping process – their rough surfaces rub against one another, and dust starts to accumulate.
This dust can be a nuisance, but it also poses a danger to your hydroponic system if you don’t rinse it out of the pebbles before use. When clay dust becomes wet, it can start to clog parts of your hydroponic system, which is something you should avoid if at all possible.
Another possible downside of this medium is the fact that it does drain quickly. For certain types of plants, this is a very good thing. If you raise plants that need a large amount of water, clay may drain too quickly and cause them to dry out. And if you aren’t familiar with the needs of any plant you want to grow, make sure you investigate them before committing to any growth medium.
If you intend to move your hydroponic setup (or parts of it) at any time, it might be helpful to know that clay pebbles can become very heavy when soaked in water. This is a little surprising for some first-time users – since the pebbles are porous, they feel very lightweight when they arrive. But as they fill with water, they can be very heavy.
If you’re environmentally conscious, you may hesitate to use clay pellets. This is because manufacturers obtain clay through strip mining. Strip mining is a process that damages the environment considerably – bulldozers remove the top layer of earth in order to dig up the clay beneath it.
What Size Should You Get?
As you search for clay pebbles for your hydroponic setup, you may be wondering which size is ideal. Companies offer pebbles from 4mm in diameter to over 16mm, and some are even smaller or larger. What size you choose will depend on what types of plants you’re growing. Larger pellets are ideal for plants that need less water – larger pebbles have more space between them and water drains faster. Smaller pebbles pack in closer and drain more slowly. To use pebbles to start seeds but need more water retention, you can crush the pebbles to make smaller pieces. The pieces will still be porous, but they will pack closely together and retain moisture more easily.
Final Thoughts
To grow a successful hydroponic garden, you’ll need to master many different variables – the design of the system itself, your components, and your growth medium. Especially if you’re new to hydroponics, we think clay pebbles are an excellent choice. They can work with almost any variety of plant, they strike a great balance between aeration and hydration, and they’re reusable. Just make sure you take your time and do your research, and you’ll be on your way to a healthy garden.
Happy Growing!
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